ULTRASOUNDING DIAPHRAGMAL THICKNESS

A small pilot study in Chest demonstrates how diaphragmal wasting can be measured using a simple ultrasound technique.

Background
One of the big challenges in intensive care is weaning patients from their ventilators. Weaning often accounts for 40-50% of the total duration of mechanical ventilation. In some patients it takes even longer.

One significant contributor to delayed weaning is ventilator-induced diaphragmatic dysfunction (VIDD). This is the diaphragmal muscle wasting that is a consequence of critical illness, critical illness neuropathy and mechanically offloading the diaphragm.

Then, when our patient needs his diaphragm again it has wasted away so much it can´t generate the force necessary of efficient breathing. VIDD now results in failed extubations, failed spontaneous breathing tests and delayed weaning.

We could use a reliable method for identifying diaphragmal wasting. This could help us predict failed weaning and plan our next steps accordingly.

The study
The study explores using ultrasound for motoring and quantifying diaphragmal thinning. The authors recorded daily measurements from the day of intubation until the patient was extubated, had a tracheostomy or died. It is a small study. Just seven patients.

Ultrasound technique
The mechanichally ventilated patients were seated upright at a 90-degree angle.

Then the probe was placed in the right mid-axillary line. The diaphragm was identified as a three-layered structure just above the liver.

This structure is the diaphragmatic pleura, the non-echogenic diaphragm and the peritoneal pleura. Diaphragmal thickness was defined as the distance between the middle of the pleuras.

Images and measurements were obtained at end-expiration

ResultsDiaphragmal thinning started within 48 hours in all patients and then proceeded in an almost linear fashion.

On average, diaphragmal thickness decreased by 6% per day on mechanical ventilation.

Take home message
Diaphragmal thickness and wasting can possibly be measured and motored using a standardised ultrasound technique.

Interesting concept, but to be really useful a diaphragmal thinning index must be correlated to some useful parameter like the chance of successful weaning, force generated by the diaphragm etc.

Subscribe to Blog via Email

Email Address

About ScanCrit

A blog on anaesthesia, intensive care and emergency medicine. In-hospital and outside. Mostly focusing on the critically ill patient. Written by two Scandinavian senior anaesthetic registrars turned consultants.

This is our way of keeping log of articles and interesting things we come across in our work and on the internet. Should any of you out there stumble across this blog and find it useful then all the better.

Please leave comments or questions if you have any. The best way to keep learning is to keep the conversation going.